Method of chilling or freezing products in a cryogenic spiral freezer

ABSTRACT

An upwardly helical flow path of cryogen-rich air inside a cryogenic spiral freezer may be used to chill or freeze products.

CROSS-REFERENCE TO RELATED APPLICATIONS

None.

BACKGROUND

Typically, cryogenic spiral freezers (spirals) have fans placed in twoand a half corners of the often-square-shaped spiral enclosure. Aconveyor belt feeds into the spiral via an opening (the inlet) in thehousing located at one of the corners (the starting corner). Thestarting corner typically has room for a fan or fans only at positionswell above the inlet. An adjacent corner constitutes the exit portion.The exit portion includes an opening in the housing (the outlet) fromwhich the conveyor belt emerges for unloading of chilled products. Theexit portion also includes a device (take-up tower) for providingtension to the portion of conveyor belting returning to the front of thespiral. Typically, there is no room near the take-up tower for fans.Thus, the remaining two corners are often the only areas that havesufficient room to mount fans directing air to all levels of the spiral.As a result of this fan placement, as the spiral belting revolves, adirect and aggressive airflow is directed across the belt only two, andsometimes three, times per revolution of the belt as the product to bechilled passes directly in front of a fan. Since a spiral freezer relieson aggressive airflow to achieve maximum heat transfer between theflowing cold vapor and the relatively warm product, this means that fora significant percentage of each revolution of the belt, the productdoes not receive the full advantage provided by exposure to anaggressive airflow.

Thus, there is a need in the art to provide spiral freezers that allow agreater number of exposures of products to an aggressive airflow perbelt revolution.

Typically, the corner fans in a spiral direct airflow across the widthof the belt. In other words, the above-mentioned aggressive airflow isin a direction perpendicular to the travel direction of the belt. Due toturbulence caused by impingement of the airflow onto the belting supportmember, the belting, and the product, the velocity of the airflowdiminishes as the airflow travels from the outer portion of the belt andacross the product to the inner portion of the belt. As a result,product placed on an outer side of the conveyor belting is exposed to ahigher airflow velocity than product placed on an inner side of theconveyor belting. Thus, a temperature gradient is created where moreheat is removed from the outermost product than the innermost product.This temperature gradient across the belt can impact the quality offreezing that the products on the inside receive, or cause the operatorto over-freeze the outside product in order to achieve satisfactoryresults on the inside.

Thus, there is a need in the art to provide spiral freezers that allow agreater uniformity of freezing for products across the width of theconveyor belt.

Cryogenic spiral conveyors are normally enclosed within a largerectangular, insulated structure. Because of the nature of the cryogenicvapor (whether CO₂ or N₂), the coldest, densest gas falls to the floorof the spiral. Typically, the conveyor belting entrance to the spiral islocated at floor level. Thus, it is the natural tendency of the coldvapor to escape out that opening (the path of least resistance). As thecoldest vapor leaves the spiral, it causes a “siphon effect” such thatwarm air is sucked into the enclosure through the exit opening for thespiral conveyor belting. This “warm air infiltration” causes a reductionin the heat transfer rate of the freezer, and is countered by injectinglarger amounts of cryogen just to maintain the temperatures necessary tofreeze the product. Warm air infiltration also introduces room air andhigher moisture levels in the spiral enclosure, leading to a buildup ofhighly undesirable water ice on all the cold surfaces within the spiralas well as the product. Warm air infiltration increases the cryogenicfreezing cost and reduces productivity.

Thus, there is a need in the art to provide spiral freezers that avoidor reduce undesired buildup of water ice on product and cold surfacesand increased cryogenic freezing costs.

Cryogenic spiral conveyors are normally enclosed within a largerectangular, insulated structure. The enclosure is normally longer onthe side that contains the take-up tower. The spiral belting is drivenby a combination of a center drum, normally made up of a cage design,and a take-up drive located in the take-up tower system. On many smallerto medium spiral freezers, there are no access doors to the freezerenclosure on the narrow ends of the rectangle. This means that there isvery limited space for maintenance on the narrow ends of the enclosure,and sanitation can only be achieved through a high pressure spray. Also,the inside of the drum is virtually inaccessible. Limited access meansthat in worst cases, a partial disassembly of the spiral is necessary(for drum cage wear strip maintenance), and the inside portions of thebelting and support structure are outside of arm's reach on the narrowends of the rectangular enclosure for purposes of maintenance orsanitation. Limited access means inadequate sanitation, excessivevolumes of hot water and energy for sanitation, and excessivemaintenance time and cost.

Thus, there is a need for spiral freezers that provide increased ease ofaccess to freezer interiors, increased sanitation, increased ease ofsanitation, lower hot water and energy usage, and decreased maintenancetime and cost.

SUMMARY

There is also provided a method of chilling or freezing products in aspiral freezer. The method comprises the following steps. A plurality ofitems are introduced onto a conveyor belt that moves in a helical pathwithin a spiral freezer. Cryogen is injected into a flow of chilled airin the spiral freezer to provide cryogen-rich air. The cryogen-rich airflows along a helical flow path above and parallel to the helical pathof the conveyor belt within the spiral freezer.

There is provided a cryogenic spiral freezer, comprising: a rotatabledrum; a conveyor belt support spiraling up and around the drum to form aspiral ramp, each full revolution of the conveyor belt support aroundthe drum constituting a tier, the conveyor belt support not beingconnected to the rotatable drum; an endless conveyor belt disposed ontop of the conveyor belt support along a helical path; a cryogeninjection apparatus comprising a feed line leading to at least onemanifold extending in between adjacent tiers of the conveyor beltsupport, each of said at least one manifold including at least onenozzle positioned and configured to inject cryogen downwardly towardsthe conveyor belt; a cylindrical freezing chamber housing enclosing thedrum, and conveyor belt support; and a blower apparatus comprising atleast one blower each one of which is associated with a correspondingblower inlet and a corresponding blower outlet. Each of said at leastone blowers is adapted and configured to draw in cryogen-rich air fromthe corresponding inlet and blow cryogen-rich air out of thecorresponding outlet to induce a helical flow path of cryogen-rich airabove and parallel to the helical path of the conveyor belt.

The cryogenic spiral freezer or method may include one or more of thefollowing aspects:

-   -   the helical flow of the cryogen-rich air is above and parallel        to the helical path of the conveyor belt along the entire        helical path of the conveyor belt.    -   the helical flow path of the cryogen-rich air is upward and in a        same direction as travel of the conveyor belt along the helical        conveyor belt path.    -   the conveyor belt travels its helical path while supported by an        upwardly spiraling conveyor belt support; and the helical flow        of the cryogen-rich air is constrained above and below by        adjacent tiers of the conveyor belt support.    -   the conveyor belt rotates around and up a cylindrical drum        disposed in a center of the spiral freezer along the helical        path; the drum has a continuous outer surface that prevents a        flow of gas into an interior of the drum; the spiral freezer        comprises a cylindrical freezing chamber housing that encloses        the conveyor belt along its helical path; and the helical flow        of the cryogen-rich air is constrained on one side by the        continuous outer surface of the drum and constrained on an        opposite side by the freezing chamber housing.    -   the conveyor belt travels its helical path while supported by an        upwardly spiraling conveyor belt support; a blower apparatus        comprises at least first and second blowers each one of which        includes a blower inlet and a blower outlet; the inlet of the        first blower receives cryogen-rich air from a first portion of        the spiral freezer in between adjacent tiers of the conveyor        belt support and blows it from the outlet of the first blower        into a second portion of the spiral freezer in between adjacent        tiers of the conveyor belt support; and the inlet of the second        blower receives cryogen-rich air from a third portion of the        spiral freezer in between adjacent tiers of the conveyor belt        support and blows it from the outlet of the second blower into a        fourth portion of the spiral freezer in between adjacent tiers        of the conveyor belt support.    -   the cryogen-rich air blown from the outlet of the first blower        outlet flows along an axis that, when said axis crosses a        midpoint of the helical path, said axis is parallel to the        tangent line of the helical path.    -   the cryogen-rich air blown from the blower outlets is blown in a        direction that is never perpendicular to a direction of travel        of the portion of the conveyor belt traveling directly        underneath the blown cryogen-rich air.    -   the conveyor belt has a middle portion in between inner and        outer edges; the conveyor belt rotates around and up a        cylindrical drum disposed in a center of the spiral freezer        along the helical path through frictional engagement between the        inner edge of the conveyor belt and an outer circumferential        surface of the cylindrical drum; the conveyor belt is supported        by an upwardly spiraling conveyor belt support forming a ramp        underneath the helical path; and the inner edge and the middle        portion of the conveyor belt are continuously supported by the        conveyor belt support from a bottom of the helical path to a top        of the helical path.    -   the cryogen is liquid nitrogen.    -   the cryogen is liquid carbon dioxide.    -   via a freezing chamber housing outlet, the conveyor belt exits        the freezing chamber housing enclosing the helical path and the        helical flow path and enters into an interior of a take-up tower        housing; the conveyor belt travels over, under, and/or around a        plurality of rollers in a tensioning apparatus inside the        take-up tower housing; via a freezing chamber housing inlet, the        conveyor belt exits the take-up tower housing and enters the        freezing chamber housing; and a gaseous atmosphere inside the        interior of the freezing chamber housing is isolated from a        gaseous atmosphere inside the interior of the take-up tower        housing by a wall of the freezing chamber housing except for        flow communication via the freezing chamber housing inlet and        freezing chamber housing outlet.    -   via the freezing chamber housing outlet, allowing a portion of        the cryogen-rich air exiting the interior of the freezing        chamber housing to enter into the interior of the take-up tower        housing; and re-circulating a portion of the cryogen-rich air        exiting the freezing chamber outlet back to an interior of the        freezing chamber housing via a recirculation passageway and a        recirculation blower disposed outside the freezing chamber        housing adjacent to the freezing chamber housing outlet.    -   the drum has a continuous outer surface that prevents a flow of        gas into an interior of the drum.        -   the conveyor belt has a width W, and the freezing chamber            housing is spaced from an outer edge of the conveyor belt by            no more than 0.1 W.    -   the conveyor belt support has a continuous surface that supports        at least all portions of the conveyor belt in between inner and        outer edges of the conveyor belt and prevents a flow of gas        through the conveyor belt support.    -   the cryogenic spiral freezer further comprises:        -   a take-up tower housing;        -   plurality of rollers disposed within an interior of the            take-up tower housing that support travel of the conveyor            belt through the take-up tower housing interior, wherein:        -   the freezing chamber housing has an inlet and outlet allow            travel of the conveyor belt into and out of the freezing            chamber, respectively;        -   the freezing chamber inlet and outlet are in communication            with the take-up tower housing interior; and        -   the interior of the freezing chamber housing is isolated            from the interior of the take-up tower housing by a wall of            the freezing chamber housing except for the freezing chamber            housing inlet and outlet.    -   the cryogenic spiral freezer further comprises a pair of        parallel conveyor belt support rails supporting inner and outer        edges of the conveyor belt as it travels through the interior of        the take-up tower housing, the conveyor belt support rails        connecting with a top of the conveyor rail support to support        travel of the conveyor belt out of the freezing chamber housing        and into the take-up tower housing interior.    -   the take-up tower housing has a first opening communicating with        an exterior of the take-up tower housing to form a product exit        and a second opening communication with the exterior of the        take-up tower housing to form a product entry where chilled or        frozen product may be unloaded from the conveyor belt;    -   said spiral freezer further comprises a rear-most roller        receives that travel of the conveyor belt therearound at a        position located adjacent the product exit and a front-most        roller that receives travel of the conveyor belt therearound at        a position located adjacent the product entry where product to        be chilled or frozen may be loaded onto the conveyor belt.    -   the cryogenic spiral freezer further comprises a recirculation        blower disposed adjacent the freezing chamber outlet and a        recirculation passageway defined by an outer surface of the        freezing chamber housing and an outer surface of a concave        portion of the take-up tower housing, the recirculation        passageway providing a gas flow passage communicating between        the freezing chamber outlet and one or more air return openings        formed in the freezing chamber housing, the recirculation blower        oriented to draw in a portion of cryogen-rich air exiting the        freezing chamber outlet and blow the drawn-in portion into the        recirculation passageway.    -   said blower assembly comprises a plurality of blowers each one        of which being associated with a blower inlet and a blower        outlet, and said blower inlets are vertically aligned at one        radial position with respect to an axis of the freezing chamber        housing and said blower outlets are vertically aligned at        another radial position with respect to the axis of the freezing        chamber housing.    -   each of said blowers is driven by a common blower motor drive        shaft which in turn is driven by a single blower motor.    -   each of said at least one blower is disposed outside the freezer        chamber housing.    -   the conveyor belt support has a dimpled surface.    -   the conveyor belt has a midline equidistant from inner and outer        edges of the conveyor belt;    -   each of said at least one blower outlets is oriented along a        corresponding axis; and    -   each of said at least one axes extends over the midline of the        helical path parallel to a line tangent to the midline.    -   the induced helical flow of the cryogen-rich air is above and        parallel to the helical path of the conveyor belt along the        entire helical path of the conveyor belt.    -   the conveyor belt has a midline equidistant between inner and        outer edges of the conveyor belt;    -   the conveyor belt rotates around and up a cylindrical drum        disposed in a center of the spiral freezer along the helical        path through frictional engagement between the inner edge of the        conveyor belt and an outer circumferential surface of the        cylindrical drum; and    -   the midline of the conveyor belt is continuously supported by        the conveyor belt support from a bottom of the helical path to a        top of the helical path.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further understanding of the nature and objects of the presentinvention, reference should be made to the following detaileddescription, taken in conjunction with the accompanying drawings, inwhich like elements are given the same or analogous reference numbersand wherein:

FIG. 1A is an isometric view of an embodiment of the inventive spiralfreezer taken from a point of view to the right side of and behind aproduct exit.

FIG. 1B is an isometric view of the freezer of FIG. 1A taken from apoint of view to the right side of and in front of a product entry.

FIG. 2 is an isometric view of an assembly including the drum, driveshaft, drive motor, and support structure of the freezer of FIG. 1A.

FIG. 3 is an isometric view of the assembly of FIG. 2 that also includesa conveyor belt support configured as a spiral ramp.

FIG. 4 is an isometric view of the conveyor belt and rollers of thefreezer of FIG. 1A.

FIG. 5A is an isometric view of the assembly of FIG. 3 that alsoincludes the conveyor belt and rollers of FIG. 4 and the blower assemblyand cryogen injection assembly of FIG. 1A.

FIG. 5B is an isometric view of the assembly of FIG. 5A taken from apoint of view to the right side of and in front of the product entry.

FIG. 6 is an isometric view of the blower assembly of FIG. 5A.

FIG. 7 is a rear elevation view of the assembly of FIG. 3 that alsoincludes the blower assembly of FIG. 6.

FIG. 8A is an isometric view of the freezer of FIG. 1A with the take-uptower housing and exhaust vents removed.

FIG. 8B is an isometric view of the freezer of FIG. 8A taken from apoint of view to the right side of and in front of the product entry.

FIG. 9 is an isometric view of the freezing chamber housing and blowerapparatus of FIG. 1A revealing interior features and the helical flowpath of cryogen-rich air that is taken from a point of view to the leftside of and in front of a product entry.

FIG. 10 is an isometric view of the freezer of FIG. 8A with the conveyorbelt and rollers removed.

FIG. 11 is an isometric view of the take-up tower housing of the freezerof FIG. 1A revealing interior features that is taken from a point ofview to the left side of and in front of the product entry.

FIG. 12 is an isometric view of the freezer of FIG. 1A revealinginterior features that does not include the blower apparatus, supportlegs and arms, cryogen injection apparatus, conveyor belt, rollers, orexhausts that is taken from a point of view to the right side of andbehind a product exit.

DETAILED DESCRIPTION

The inventive freezer allows products to be chilled or frozen bysubjecting them to a flow of cold cryogen-rich air inside a spiralfreezer. The flow of cryogen-rich air follows the same helical path asthe conveyor belt and thus is co-current to the travel direction of theconveyor belt. The helical flow path of the cryogen-rich air is producedby a plurality of blowers each one of which separately receivescryogen-rich air from in between adjacent tiers of the conveyor beltfrom one portion of the freezer and blows it into a different portion ofthe freezer in between adjacent tiers of the conveyor belt. The flow ofthe cryogen-rich air blown by the blowers follows a flow path that istangent to the travel direction of the conveyor belt. The spiralenhanced or maintained by restricting its ability to flow through theconveyor belt, by restricting its ability to flow through the drum, andby restricting its ability to flow out of an area in between adjacenttiers of the conveyor belt travel.

The inventive freezer may be used to chill or freeze a wide variety ofproducts, including foodstuffs and other industrial products. Thefoodstuffs include but are not limited to meat, poultry, seafood,produce, sauces, ready-to-eat meals, and ready-to-cook meals.

As best illustrated in FIGS. 1A and 1B, an embodiment of the inventivespiral freezer includes a freezing chamber housing 1 that is connectedto a take-up tower housing 5 containing a conveyor belt tensioningapparatus. Inner surfaces of the freezing chamber housing 1 define afreezing chamber. While the freezing chamber and take-up tower housings1, 5 may be constructed of any material used for such purposes in thefield of spiral freezers, typically they are constructed of moldedinsulated fiberglass for ease of manufacture and lowered material costs.

A conveyor belt 9 receives product to be chilled or frozen at a positionadjacent to a product entry 13 and yields chilled or frozen product at aproduct exit 17. A take-up tower exhaust 21 and an inlet exhaust 25 areused to exhaust cryogen-rich air to vent. A blower assembly 29 induces aspiral flow path for cryogen-rich air inside the freezing chamber. Arecirculation blower (not illustrated) is disposed at an upper portionof a recirculation passageway 33 that re-circulates cryogen-rich airfrom an upper portion of the take-up tower housing to the interior ofthe freezing chamber via a plurality of openings in the freezing chamberhousing 1. The cryogen-rich air is produced by injecting cryogen intothe freezing chamber via a cryogen injection apparatus 37.

The cryogen may be liquid nitrogen. As the cryogen is injected from thecryogen injection apparatus 37 into the gaseous atmosphere of thefreezing chamber, the substantial latent heat of vaporization of thenitrogen cools the atmosphere inside the freezing chamber. Also,nitrogen still in liquid form may impinge surfaces of the product to bechilled or cooled. The latent heat of vaporization of the impingingnitrogen cools the product. Moreover, the significant sensible heatremaining in the vaporized nitrogen helps to cool both the product andthe atmosphere through heat exchange.

Alternatively, the cryogen may be liquid carbon dioxide. In this case,the liquid carbon dioxide exits the cryogen injection apparatus 37 inthe form of low-temperature CO₂ snow and low-temperature CO₂ vapor. Thesubstantial heat of sublimation of the solid CO₂ snow cools theatmosphere inside the freezing chamber. Any solid CO₂ snow that impingesupon the surfaces of product also cools the product by the samemechanism. Similar to the use of nitrogen as the cryogen, thesignificant sensible heat remaining in the sublimated carbon dioxidehelps to cool both the product and the atmosphere through heat exchange.

When the inventive freezer is used for chilling or freezing foodstuffs,the liquid nitrogen or liquid carbon dioxide are food-grade liquidnitrogen or food-grade liquid carbon dioxide.

A drum motor 41 rotates a drum (hidden) contained within the freezingchamber housing via a spindle 45. The drum is supported by receiving atop portion of the spindle in an upper bearing 49 and a lower bearing(hidden). The upper bearing 49 is in turn supported by a plurality ofsupport arms 53 that lead to a corresponding plurality of support legs57 that are connected to a blower motor 65. The support legs 57 and thelower bearing are secured to a base 69. While FIGS. 1A and 1Billustrated three support arms 53 and legs 57, one of ordinary skill inthe art will recognize that more or fewer may be utilized.

As best shown in FIG. 2, a cylindrical drum 42 is rotated by the spindle45 which is secured to and extending through an axis of the drum 42. Thespindle 45 is driven by the drum motor 41 and extends between the upperand lower bearings 49, 73. As best illustrated in FIG. 3, conveyor beltsupport 77 extends in a spiral path around the drum 42 to form a spiralramp. The conveyor belt support 77 is not connected to the drum 42 sothat the conveyor belt support 77 remains stationary during rotation ofthe drum 42. Each revolution of the conveyor belt support 77 constitutesone tier. Thus, in FIG. 3, ten tiers are illustrated. As best shown inFIG. 4, the conveyor belt 9 is guided via a plurality of rollers 10where one or more of the rollers 10 is rotated with a drive motor (notillustrated) to urge travel of the conveyor belt around, over, or underthe rollers 10 in a belt travel direction. While the conveyor belt 9 maybe constructed of any material used for conveyor belts in the field ofspiral freezers, including a metal such as stainless steel, typically itis constructed of polyethylene, such as UHMW, or other polymer materialhaving similar physical properties.

As best illustrated in FIGS. 5A and 5B, a suitable amount of tension isapplied to the conveyor belt 9 by maintaining an appropriate amount ofspace in between at least one pair of adjacent rollers 10. The tensionapplied to the conveyor belt 9 causes an inner edge of it tofrictionally engage a circumferential surface of the drum 42 so that, asthe drum 42 is rotated by the drum motor 41 via the spindle 45, theconveyor belt 9 is driven in a spiral path on top of the conveyor beltsupport 77 around and up the drum 42. The conveyor belt 9 completesseveral revolutions around the drum 42, each one of which constitutes atier. While FIGS. 5A and 5B illustrate nine tiers, one of ordinary skillin the art will recognize that more or less tiers may be utilized basedupon the residence time desired within the freezing chamber. Theconveyor belt support 77 may be constructed of any material used in thefield of spiral freezers, including a metal such as stainless steel or apolyethylene (such as UHMW) or other polymer material having similarphysical properties. Typically, when the conveyor belt 9 is made of apolymer material, the conveyor belt support 77 is made of stainlesssteel and when the conveyor belt 9 is made of stainless steel, theconveyor belt support 77 is made of a polymer material.

As best shown in FIGS. 5A, 5B, 6, and 7, the freezer includes a blowerassembly 29 includes the blower motor 65 that drives a plurality ofblowers 66A, 66B, 66C via a common drive shaft 71. The blowers 66A, 66B,66C may be of any type in the field of gas handling. Typically, they areof the impeller type that receives an axial flow of air and ejects itwith a radial flow. Each blower 66A, 66B, 66C includes a blower inlet68A, 68B, 68C that receives cryogen-rich air from in between adjacenttiers from one portion of the freezing chamber and a blower outlet 67A,67B, 67C that blows the cryogen-rich air over the conveyor belt 9 inbetween adjacent tiers from a different portion of the freezing chamberin a direction parallel to the travel direction of the conveyor belt 9.Except for the portions of the blower inlets 68A, 68B, 68C and bloweroutlets 67A, 67B, 67C disposed inside the freezing chamber in betweenadjacent tiers of the conveyor belt support 77, the remainder of theblower assembly 29 is typically located outside the freezing chamber inorder to avoid contamination of the interior of the freezing chamberwith motor oil from the blower motor 65. It is also typically done toallow operation of the mechanical portions of the blowers 66A, 66B, 66Cat temperatures higher than that of the interior of the freezingchamber.

While FIGS. 5A, 5B, 6, and 7 illustrate three blowers 66A, 66B, 66C, oneof ordinary skill in the art will recognize that more or fewer may beutilized depending upon the strength of the spiral gas flow pathdesired. Also, while FIGS. 5A, 5B, 6, and 7 illustrate that the inlets68A, 68B, 68C and outlets 67A, 67B, 67C of each of the blowers 66A, 66B,66C are arranged in parallel and are designed to receive and blowcryogen-rich air from portions of the freezer spaced 180° from oneanother, one of ordinary skill in the art will recognize that they neednot be spaced 180° apart. Rather, any angular spacing less than orgreater than 180° is possible so long as the size of the blower 66A,66B, 66C allows such a configuration. However, they are typically spacedfrom one another by 180°. Moreover, while FIGS. 5A, 5B, 6, and 7illustrate that each one of the blower inlets 68A, 68B, 68C of aparticular blower 66A, 66B, 66C is higher than the associated one of theblower outlets 67A, 67B, 67C by two tiers of the conveyor belt support77 (more precisely the vertical distance separated by 1.5 revolutions ofthe conveyor belt support 77), one of ordinary skill in the art willrecognize they need not be separated by more than tier and that,alternatively, they may be separated by more than two tiers.Furthermore, while FIGS. 5A, 5B, 6, and 7 illustrate a single set ofvertically aligned blowers 66A, 66B, 66C, one of ordinary skill in theart will recognize that one more than one set of vertically alignedblowers 66A, 66B, 66C may be utilized and that the blowers 66A, 66B, 66Cin general need not be vertically aligned. Typically, the blowers 66A,66B, 66C are vertically aligned so that they may be driven by a commondraft shaft 71.

As best illustrated in FIGS. 5A, 5B, and 7 the freezer also includes acryogen injection apparatus 37 that includes a vertical feed line 38that leads to plurality of horizontal manifolds 39. It should be notedthat, in an effort to achieve clarity in the FIGS, the conveyor belt 9is not illustrated in FIG. 7. Each of the manifolds 39 includes one ormore injection nozzles (not illustrated) that are adapted and configuredto inject cryogen downwardly toward the product on the conveyor belt 9.Typically, there are several injection nozzles that are equally spacedalong each of the manifolds 39 across the width of the conveyor belt 9in order to achieve uniform chilling or freezing across the width of theconveyor belt and avoid the chilling or freezing gradient problemexperienced by many conventional cryogen spirals. While the FIGSillustrate four manifolds 39, one of ordinary skill in the art willrecognize that fewer (as few as one, two or three) or more may beutilized. Such a one will also recognize that each of the manifolds 39need not be vertically aligned and more than one set of verticallyaligned manifolds 39 may be utilized. Typically, the manifolds areeither vertically aligned or radially spaced around the conveyor beltsupport 77.

As best shown in FIGS. 8A and 8B, the conveyor belt 9 is supported by aplurality of rollers 10. Product (not illustrated) to be chilled orfrozen is deposited upon the conveyor belt 9 at a point in between theforward-most roller 10 and an inlet 14 in the freezing chamber housing1. Inside the freezing chamber housing 1, the conveyor belt 9 with theproduct is wound around the drum 42 (hidden in FIGS. 8A, 8B) in a spiralpath on top of the conveyor belt support 77 (hidden in FIGS. 8A, 8B).The travel direction of the conveyor belt 9 is upwardlycounter-clockwise, but one of ordinary skill in the art will recognizethat an upwardly clockwise travel direction can instead be utilized withthe appropriate arrangement of the conveyor belt support 77 and otherrelated features.

After reaching the top tier of the spiraled conveyor belt support 77,the conveyor belt 9 exits the freezing chamber housing through an outlet18 and enters the interior of the take-up tower 5 enclosed by thetake-up tower housing 5. The conveyor belt 9 then travels out of theproduct exit 17 (not shown in FIGS. 8A, 8B) where chilled or frozenproduct is removed from the conveyor belt 9 and around the rear-mostroller 10. The conveyor belt returns through the product exit 17 andinto an interior of the take-up tower housing 5. After travel throughthe series of rollers 10 providing the suitable tension, the conveyorbelt 9 travels out of the product entry 13 (not shown in FIGS. 8A, 8B)and around a forward-most roller 10 where it is once again loaded withproduct to be chilled or frozen.

One of ordinary skill will recognize that conveyor belts in spiralfreezers actually follow a cylindrical helix path. The cryogen-rich airinside the freezing chamber of the inventive freezer follows that samehelical conveyor belt path in between adjacent tiers of the conveyorbelt support. As best illustrated by FIG. 9 where the freezing chamberhousing 1 is depicted as transparent, the cryogen-rich air follows anupwardly helical flow path 80 inside the housing 1. When viewedalongside FIGS. 3, 5A, 5B, and 7, it is evident that the upwardlyhelical flow path 80 of the cryogen-rich air is above and parallel tothe helical path that the conveyor belt 9 takes over the conveyor beltsupport 77. Thus, the flow path 80 of the cryogen-rich air is co-currentwith a travel direction of the conveyor belt 9. This novel helical flowpath 80 for the chilled air provides three main advantages.

First, the product is effectively cooled by the inventive freezer thanwith conventional spiral freezers for a given level of heat to beremoved from the product. Because the flow of cryogen-rich air is now acontinuous helical flow co-current to the direction of the producttravel, exposure of the product to an aggressive airflow issignificantly increased. As a result, the effectiveness of the heattransfer is increased. Stated another way, for a given amount ofinjected cryogen, the inventive freezer has a higher chilling orfreezing capacity. This allows a processor to increase production.Stated yet another way, for a given amount of product, the almostcontinuous exposure of the product to an aggressive airflow allows lesscryogen to be consumed for a given amount of heat for lower processingcosts.

Second, the product receives higher quality freezing from the inventivefreezer than with conventional spiral freezers for a given level of heatto be removed from the product. Because the flow of cryogen-rich air isnot perpendicular to the direction of travel of the conveyor belt, theproblem of over-chilling of product placed near an outer edge of thebelt and under-chilling of products placed near an inner edge of thebelt is avoided. Thus, there is greater uniformity of product freezingfrom belt edge to belt edge. In the context of the chilling of foodproducts, uniformity of chilling is important for achievement of adesired appearance and texture in the chilled or frozen product.

Third, the inventive freezer tends to reduce the siphon effectexperienced by many conventional cryogenic spiral freezers. Because theinlet of the conveyor belt into the spiral freezer is located at floorlevel, the cold, denser gas wants to escape out that opening. As thecoldest gas leaves the spiral freezer, warm air is sucked into theoutlet of the spiral freezer by a siphoning effect. The warm airinfiltration causes a reduction in the refrigeration capacity of thecryogen thereby necessitating the injection of additional amounts ofcryogen for purposes other than chilling the product. The inventivefreezer works against this problem (that is otherwise experienced byconventional cryogenic spiral freezers) by creating a flow of chilledair in the direction opposite that of the siphon. Because warm airinfiltration also introduces moisture into the freezing chamber, theinventive freezer tends to avoid the degree of highly undesirable waterice buildup on all the cold surfaces that is experienced by conventionalcryogenic spiral freezers.

The helical flow of cryogen-rich air is created by a pull-push effect ofthe blower apparatus 29. At a location in between adjacent tiers at oneside of the freezing chamber, the cryogen-rich air is drawn inside theinlet 68A, 68B, 68C of one of the blowers 66A, 66B, 66C and redirectedto a location in between adjacent tiers on another side of the freezingchamber from the associated outlet 67A, 67B, 67C at a position lowerthan where the cryogen-rich air was drawn in. This pull-push effect ofthe blower assembly 29 induces the helical flow path 80 of thecryogen-rich air in between adjacent tiers of the conveyor belt support77 from the bottom-most tier to the top-most tier.

The helical flow path 80 of the cryogen-rich air is maintained orenhanced by enclosing it in between the outer circumferential surface ofthe drum 42 and the inner surface of the cylindrical freezing chamberhousing 1. In contrast to conventional spiral freezers having drums withporous circumferential surfaces to allow chilled air to pass through thedrum 42, the drum 42 of the inventive freezer is for the most partsealed and its outer circumferential surface is continuous. Thus, themomentum of the helical flow of cryogen-rich air is not decreased byflow of the cryogen-rich air into the interior of the drum 42 and arestricted channel in between the drum 42 and freezing chamber housing 1is provided. Utilization of a drum 42 with a continuous outer surfaceavoids the sanitation issues experienced by conventional cryogenicspiral freezers having porous drums. As discussed in the Background, theinside of a conventional spiral freezer drum is virtually inaccessible.Limited access means that, for the worst cleanup situations, a partialdisassembly of the conveyor support rail structure is necessary forconventional cryogenic spiral freezers. The helical flow path 80 of thecryogen-rich air is further enhanced by only allowing a relatively smallgap in between an outer edge of the conveyor belt 9 and an inner surfaceof the freezing chamber housing 1. Typically, for a conveyor belt 9having a width W, an inner surface of the freezing chamber housing 1 isspaced from an outer edge of the conveyor belt 9 by no more than a gapof 0.1 W.

The helical flow path 80 of the cryogen-rich air is also maintained orenhanced by enclosing it in between adjacent tiers of the conveyor beltsupport 77. In contrast to conventional spiral freezers having a pair ofparallel conveyor support rails supporting only the inner and outeredges of the conveyor belt, the conveyor belt support 77 of theinventive spiral freezer substantially supports the entire width of theconveyor belt 9.

Substantially supporting the entire width of the conveyor belt 9 meansthat most of the surface of the conveyor belt 9 (including its middleportion and portions in between its middle and its inner and outeredges) is supported by the conveyor belt support 77 and that the flow ofcryogen-rich air through the conveyor belt 9 is inhibited. Typically,the conveyor belt support has a continuous upper surface from an inneredge to an outer edge of the conveyor belt 9. The conveyor belt supportmay optionally have a discontinuous surface whereby an otherwisecontinuous surface includes a uniform distribution of openings so that,while the surface of the conveyor belt support 77 is not perfectlycontinuous, it does support the middle of the conveyor belt 9 (as wellas portions of the conveyor belt 9 in between the middle and the edges)and also inhibits a flow of the cryogen-rich air through the conveyorbelt 9.

Additionally, one of ordinary skill in the art will recognize that theinner and outer edges of the conveyor belt 9 may project somewhatinwardly and outwardly, respectively, from the conveyor belt support 77without departing from the invention or impeding the creation of thehelical flow path 80 of cryogen-rich air. Thus, there may be a limitedgap in between the drum and an inner edge of the conveyor belt support77 and/or the outer edge of the conveyor belt 9 may be unsupported.

The conveyor belt support 77 may optionally have a dimpled surface sothat wear of the conveyor belt support 77 and conveyor belt 9 isminimized. If that feature is desired, the conveyor belt 9 contacts onlythe top surfaces of the dimpled portions of the conveyor belt support77.

Although the conveyor belt support 77 is illustrated as providingcontinuous support to the conveyor belt in the travel direction of thebelt 9 as it travels from the bottom of the drum 42 to the top of thedrum 42, one of ordinary skill in the art will recognize that theinventive spiral freezer may utilize individual tiers of conveyor beltsupports 7 that sandwich and connect one or more tiers of conventionalconveyor belt support rails (a parallel pair of rails that only supportthe inner and outer edges of the conveyor belt 9). For example, theconveyor belt 9 may be supported across substantially its entire widthfor one revolution the conveyor belt support 77 immediately upon entryinto the freezing chamber. At the termination of this first revolution,the conveyor belt support 77 may connect with a pair of conventionalconveyor belt support rails for one or even two or more revolutionsaround the drum so that the conveyor belt 9 travels upon rails insteadof the conveyor belt support 77. At the termination of that revolutionor those revolutions, the conveyor belt 9 can once again be supportedacross substantially its entire width by the conveyor belt support 77.This sequence of conveyor belt support 77 and pair of parallel conveyorbelt support rails can be repeated up to the top of the spiral freezer.

As best illustrated in FIGS. 1A, 1B, 10, 11, and 12, a portion of theflow of cryogen-rich air exiting the freezing chamber outlet 18 isdirected downwardly into the re-circulation passageway 33 by therecirculation blower 36. The re-circulation passageway 33 is formed byan outer surface of the freezing chamber housing 1 and an inner surface32 of a concave, wedge-shaped portion of the take-up tower housing 5.The cryogen-rich air in the re-circulation passageway 33 is returned tothe freezing chamber via a plurality of return air inlets 34 formed inthe freezing chamber housing 1.

As best shown in FIGS. 11 and 12, the take-up tower housing 5 is adaptedand configured to fit together with the freezing chamber housing 1 incomplementary fashion. Edges 6 of walls of the take-up tower housing 5define a front opening 8 that opens into an interior of the take-uptower housing 5. The outer surface of the freezing chamber housing 1nestles inside the front opening 8 and against the edges 6 to preventair from infiltrating in between the edges 6 and outer surfaces of thefreezing chamber housing 1.

With reference to each of the FIGS, in operation, the conveyor belt 9travels up and around the forward-most roller 10 after which product tobe chilled or frozen is loaded upon it. The loaded conveyor belt 9 withproduct enters product entry 13 which is an opening in a front face ofthe take-up tower housing 5. After traversing a short distance, theloaded conveyor belt 9 then enters the inlet 14 of the freezing chamberhousing 1.

The product on the conveyor belt 9 is immediately subjected to aninjection of cryogen from nozzles (not illustrated) formed in thebottom-most manifold 39 of cryogen injection apparatus 37. Aftertraveling one revolution around the drum 42 (hence, traveling one tier),the conveyor belt 9 passes underneath the outlet 67A of the bottom-mostblower 66A. The flow of cryogen-rich air blown from the outlet 67A iscentered upon an axis that is tangent to travel direction of theconveyor belt 9. The conveyor belt 9 then travels one more revolutionaround the drum 42 where it is again subjected to an injection ofcryogen from the nozzles of the manifold 39. The conveyor belt 9 thentravels one-half a revolution around the drum 42 where it passesunderneath the inlet 68A of the bottom-most blower 66A. The conveyorbelt 9 then 1.5 more revolutions around the drum 42 where it passesunderneath the outlet 67B of the middle blower 66B and is againsubjected to an injection of cryogen from the nozzles of the manifold39. The conveyor belt 9 then travels 1.5 more revolutions around thedrum 42 where it passes underneath the inlet 68B of the middle blower66B. The conveyor belt 9 then travels one-half a revolution around thedrum 42 where it is again subjected to an injection of cryogen frommanifold 39. The conveyor belt 9 then travels one more revolution aroundthe drum 42 where it passes underneath the outlet 67C of the top-mostblower 66C. The conveyor belt 9 then travels one more revolution aroundthe drum 42 where it is again subjected to an injection of cryogen frommanifold 39. The conveyor belt then travels one-half a revolution morearound the drum 42 and passes underneath the inlet 68C of the top-mostblower 66C. After traveling one-half a revolution more around the drum42, the conveyor belt 9 has reached the top tier of the conveyor beltsupport 77 and exits the outlet 18 of the freezing chamber housing 1.

One of ordinary skill in the art will recognize that, while the conveyorbelt 9 is traveling up and around the drum 42 it is subjected to a flowof cryogen-rich air flowing in a helical flow path 80 co-current to thetravel direction of the conveyor belt 9.

After exiting the outlet 18, the conveyor belt 9 immediately emergesinto the interior of the take-up tower housing 5. Upon leaving theoutlet 18, the conveyor belt 9 is no longer supported by the conveyorbelt support 77 but is instead supported by conventional conveyor beltsupport rails (not illustrated). Because the conveyor belt 9 is nolonger supported by the conveyor belt support, a portion of thecryogen-rich air at the top of the spiral freezer (which tends to be iscolder than the atmosphere inside the take-up tower housing 5) exits thefreezing chamber at the freezing chamber outlet 18 and spills downthrough the conveyor belt 9 to the bottom portion of the interior of thetake-up tower housing 5.

By isolating the freezing chamber from the interior of the take-up towerhousing 5, the inventive spiral freezer exhibits a lower degree ofcryogen consumption for the same degree of chilling of the items in thefreezing chamber. It also tends to inhibit the accumulation of ice onsurfaces inside the freezing chamber that eventually need to be removed,thereby necessitating shutting down the chilling or freezing process.The mechanisms responsible for these advantages are two-fold.

First, because the interior of the freezing chamber is relativelyisolated from the interior of the take-up tower housing 5, there is muchlower turbulent air flow in between the two spaces. Thus, the relativelywarmer air infiltrating from the ambient atmosphere outside the productexit 17 has a greater tendency to remain trapped at an upper portion ofthe interior of the take-up tower housing 5 due to its lower densitywhile the relatively colder air spilling from the outlet 18 collects atthe lower portion of the interior of the take-up tower housing 5.

Second, because the gaseous atmosphere inside the take-up tower housing5 does not fully participate in the flow of cryogen-rich air inside thefreezing chamber, the relatively moist air infiltrating into the productexit 17 does not get mixed with the colder cryogen-rich air to the samedegree as in conventional cryogenic spiral freezers. Because there isless water vapor to condense and freeze inside the freezing chamber (incomparison to conventional cryogenic freezers), less of the cryogen isconsumed in condensing and freezing that water vapor.

These two mechanisms result in significant advantages for the inventivefreezer. When ice accumulates on surfaces in the inventive freezer, ittends to accumulate more in the interior of the take-up tower housing 5and less inside the freezing chamber. As a result, the inventive freezeris significantly easier to defrost because there are fewer surfaces todefrost inside the take-up tower housing 5 in comparison to the freezingchamber.

The conveyor belt 9 then emerges from product exit 17 which is anopening in a rear face of the take-up tower housing 5. Product isremoved from the conveyor belt 9 after which time the conveyor belt 9travels down and around the rear-most roller 10. The unloaded conveyorbelt 9 then emerges back into the take-up tower housing 5 via theproduct exit 17. The conveyor belt 9 then travels through the series ofrollers 10 providing sufficient tension. Next, the conveyor belt 9travels out the product entry 13 at the open front face of the take-uptower housing 5 and up and around the front-most roller to complete thecycle.

Apart from the sanitary advantages provided by isolating the freezingchamber from the interior of the take-up tower housing 5, the inventivefreezer is easier to clean/sanitize for other reasons. Because the drum42 is for the most part sealed, it is very difficult for food product toget inside the drum 42 from the sides, the top or the bottom. As aresult, it is ordinarily not necessary to take the spiral conveyor beltsupport 77 off of the drum 42 or to take apart the drum 42 for removalof food particles. Also, a conveyor belt support 77 that extends acrossthe side and middle portions of the conveyor belt 9 from the bottom tothe top of the drum 42 reduces the amount of food that falls from theconveyor belt 9 and onto a floor of the freezing chamber. As discussedin the Background, many conventional cryogenic spiral conveyors have noaccess doors on narrow ends of the rectangle shape enclosing thefreezing chamber and take-up tower. Because these conventional cryogenicspiral freezers have very limited space for maintenance on the narrowends of the enclosure, sanitation can only be achieved through a highpressure spray. Because the cylindrical freezing chamber housing 1 ismade up mostly of curved doors, all areas of the freezing chamber floorcan easily be flushed with minimal water and all areas of the conveyorbelt 9 and conveyor belt support 77 are within easy arm reach. As aresult, there is no need for an operator to wholly enter the interior ofthe freezing chamber housing 1—an action that is typically otherwiserequired in sanitizing conventional cryogenic spiral freezers.Additionally, all belt repairs and maintenance can be completed by anoperator while standing outside the freezing chamber housing 1. Thus,the inventive freezer avoids the problems experienced by conventionalcryogenic spiral freezers of inadequate sanitation, excessive volumes ofhot water and energy for sanitation, and excessive maintenance time andcost.

PARTS LIST

 1 freezing chamber housing  5 take-up tower housing  6 edges (of wallsof the take-up tower housing)  8 front opening (opens into an interiorof the take-up tower housing)  9 conveyor belt 10 rollers 13 productentry 14 inlet (of freezing chamber housing) 17 product exit 18 outlet(from freezing chamber housing) 21 take-up tower exhaust 25 inletexhaust 29 blower assembly 32 inner surface (of concave, wedge-shapedportion of take-up tower housing) 34 return air inlets 38 verticalconduit (I need to add to specification -oops) for cryogen 39 manifold33 recirculation passageway 37 cryogen injection apparatus 41 drum motor42 a cylindrical drum 45 spindle 49 upper bearing 53 support arms 57support legs 65 blower motor 69 base 66A, blowers 66B, 66C 67A, bloweroutlets 67B, 67C 68A, blower inlets 68B, 68C 71 common drive shaft 73lower bearing 77 conveyor belt support

Preferred processes and apparatus for practicing the present inventionhave been described. It will be understood and readily apparent to theskilled artisan that many changes and modifications may be made to theabove-described embodiments without departing from the spirit and thescope of the present invention. The foregoing is illustrative only andthat other embodiments of the integrated processes and apparatus may beemployed without departing from the true scope of the invention definedin the following claims.

What is claimed is:
 1. A method of chilling or freezing products in aspiral freezer, comprising the steps of: introducing a plurality ofitems onto a conveyor belt that moves in a helical path within a spiralfreezer; injecting cryogen into a flow of chilled air in the spiralfreezer to provide cryogen-rich air; flowing the cryogen-rich air alonga helical flow path above and parallel to the helical path of theconveyor belt within the spiral freezer.
 2. The method of claim 1,wherein the helical flow of the cryogen-rich air is above and parallelto the helical path of the conveyor belt along the entire helical pathof the conveyor belt.
 3. The method of claim 1, wherein the helical flowpath of the cryogen-rich air is upward and in a same direction as travelof the conveyor belt along the helical conveyor belt path.
 4. The methodof claim 1, wherein: the conveyor belt travels its helical path whilesupported by an upwardly spiraling conveyor belt support; and thehelical flow of the cryogen-rich air is constrained above and below byadjacent tiers of the conveyor belt support.
 5. The method of claim 1,wherein: the conveyor belt rotates around and up a cylindrical drumdisposed in a center of the spiral freezer along the helical path; thedrum has a continuous outer surface that prevents a flow of gas into aninterior of the drum; the spiral freezer comprises a cylindricalfreezing chamber housing that encloses the conveyor belt along itshelical path; and the helical flow of the cryogen-rich air isconstrained on one side by the continuous outer surface of the drum andconstrained on an opposite side by the freezing chamber housing.
 6. Themethod of claim 1, wherein: the conveyor belt travels its helical pathwhile supported by an upwardly spiraling conveyor belt support; a blowerapparatus comprises at least first and second blowers each one of whichincludes a blower inlet and a blower outlet; the inlet of the firstblower receives cryogen-rich air from a first portion of the spiralfreezer in between adjacent tiers of the conveyor belt support and blowsit from the outlet of the first blower into a second portion of thespiral freezer in between adjacent tiers of the conveyor belt support;and the inlet of the second blower receives cryogen-rich air from athird portion of the spiral freezer in between adjacent tiers of theconveyor belt support and blows it from the outlet of the second blowerinto a fourth portion of the spiral freezer in between adjacent tiers ofthe conveyor belt support.
 7. The method of claim 6, wherein thecryogen-rich air blown from the outlet of the first blower outlet flowsalong an axis that, when said axis crosses a midpoint of the helicalpath, said axis is parallel to the tangent line of the helical path. 8.The method of claim 6, wherein the cryogen-rich air blown from theblower outlets is blown in a direction that is never perpendicular to adirection of travel of the portion of the conveyor belt travelingdirectly underneath the blown cryogen-rich air.
 9. The method of claim1, wherein: the conveyor belt has a middle portion in between inner andouter edges; the conveyor belt rotates around and up a cylindrical drumdisposed in a center of the spiral freezer along the helical paththrough frictional engagement between the inner edge of the conveyorbelt and an outer circumferential surface of the cylindrical drum; theconveyor belt is supported by an upwardly spiraling conveyor beltsupport forming a ramp underneath the helical path; and the inner edgeand the middle portion of the conveyor belt are continuously supportedby the conveyor belt support from a bottom of the helical path to a topof the helical path.
 10. The method of claim 1, wherein the cryogen isliquid nitrogen.
 11. The method of claim 1, wherein the cryogen isliquid carbon dioxide.
 12. The method of claim 1, wherein: via afreezing chamber housing outlet, the conveyor belt exits the freezingchamber housing enclosing the helical path and the helical flow path andenters into an interior of a take-up tower housing; the conveyor belttravels over, under, and/or around a plurality of rollers in atensioning apparatus inside the take-up tower housing; via a freezingchamber housing inlet, the conveyor belt exits the take-up tower housingand enters the freezing chamber housing; and a gaseous atmosphere insidethe interior of the freezing chamber housing is isolated from a gaseousatmosphere inside the interior of the take-up tower housing by a wall ofthe freezing chamber housing except for flow communication via thefreezing chamber housing inlet and freezing chamber housing outlet. 13.The method of claim 12, further comprising the steps of: via thefreezing chamber housing outlet, allowing a portion of the cryogen-richair exiting the interior of the freezing chamber housing to enter intothe interior of the take-up tower housing; and re-circulating a portionof the cryogen-rich air exiting the freezing chamber outlet back to aninterior of the freezing chamber housing via a recirculation passagewayand a recirculation blower disposed outside the freezing chamber housingadjacent to the freezing chamber housing outlet.